When ‘Freddy’ Ayer asked me to contribute to his volume in the Library of Living Philosophers series , I was delighted, and while the main topic of my contribution was the sense in which it can be a ‘necessary’ truth that water is H 2 O, I devoted a section of that essay to problems that I saw with Ayer's account of the paradigm intentional notion, the notion of reference. Ayer ended his reply by saying that he could not satisfactorily meet my objections, and with characteristic modesty and good humour he added that it was only small consolation that, in his opinion, no one else could satisfactorily account for reference either. The thoughtfulness, fairness, and responsiveness of Ayer's entire reply reminded me of the way in which the same qualities were displayed in Carnap's reply to my contribution to his volume in the same series. These two replies—Carnap's and Ayer's—display the virtues of the philosopher who searches for truth, and who genuinely welcomes serious criticism, in a truly exemplary way. I treasure both of them, and they are bound up with my memories of those two wonderful philosophers